Helps offender since being impaled with stake (5)
I believe the answer is:
abets
'helps' is the definition.
(to abet is to aid or assist)
'offender since being impaled with stake' is the wordplay.
I cannot quite understand how this works, but
'stake' could be 'bet' (synonyms) and 'bet' is located in the answer.
'since' could be 'as' (both can mean 'because') and 'as' is located in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abets that I've seen before include "Helps (someone to commit crime)" , "Aids in wrong-doing" , "Assists dealer, say" , "Aids and encourages" , "Assists in wrongdoing" .)